Just a day after shaking hands on a free trade agreement, the United States and Australian Governments are in open disagreement over what they agreed to - with Australia rejecting US claims that it has promised moves to end the Australian Wheat Board's monopoly on exports.

As Trade Minister Mark Vaile estimated benefits of more than $4 billion in export gains in the next 20 years for the beef and dairy industries, meat industry experts warned that a safeguard clause inserted in the agreement by US negotiators could threaten much of those gains.

The Government yesterday strongly defended the deal as a good one for farmers, despite its leaving 25 per cent of US agricultural products protected by often high tariffs against Australian competition, and the US granting no additional access for Australian sugar.

But Government sources agreed that a transitional safeguard insisted by the US would allow tariffs to be reimposed on Australian beef even after quotas officially end some time around 2025. In a "safeguard" never employed in US free trade agreements with any other country, the US got Australia's agreement to reimpose tariffs if beef prices in the US slip by just 6.5 per cent from quarter to quarter.

A Meat and Livestock Authority spokesman was reported yesterday as saying its analysis showed that such a clause would have been triggered six times in the past decade. But a spokesman for Mr Vaile said the Government believed the safeguards would rarely apply.

In another area of confusion, the US Government has reported that Australian negotiators pledged to join with the US in the World Trade Organisation to try to eliminate restrictions on the right of firms to export. Yet Australia itself is at the centre of such restrictions, with single desk export marketing of wheat, rice and sugar.

The official US version of the deal, published on the web at www.ustr.gov, reports that: "In response to US concerns about Australia's agricultural state trading enterprises, Australia committed to working with the US in the ongoing WTO negotiations on agriculture to develop export competition disciplines that eliminate restrictions on the right of entities to export."

But a spokesman for Mr Vaile yesterday denied that Australia had made any such commitment, describing the US statement as "spin" for its constituents.

"What we agreed was to work together in the WTO to eliminate export subsidies, and to work on removing other trade-distorting measures in the area of export competition," he said. "But Australia's export, single-desk arrangements involve no subsidies, and are not trade-distorting."

Mr Vaile told Parliament that the additional export access secured under the deal would amount to a cumulative $2.6 billion for beef over the next 20 years and $1.65 billion for dairy products. In addition, the exporters would save $440 million in tariffs now paid to the US.